Video Fishing

Underwater stereo-video is a research tool that is capable of making accurate, precise, non-invasive measurements of fish length or biomass [1-8] and may have many benefits for managers of wild stock and for aquaculturalists. Comparisons of the accuracy and precision of length estimates of plastic silhouettes of fish [6,7] and real fish [8] by experienced scientific divers and stereo-video cameras have demonstrated the measurement accuracy, precision and advantages of stereo-video measurements for both length and distance estimates.

Underwater stereo-video systems consist of two or more video cameras with known, fixed focal lengths, and known distances of separation and angles of convergence of the cameras [9]. Video imagery is imported in a stereo photo comparator [10] along with camera calibration and relative orientation information. The stereo photo comparator facilitates the location of objects in three dimensional coordinates (x, y, z) relative to the position and orientation of the camera pair. These data can be used to measure distance and angle, accurately defining the extent of a sampling unit (e.g. a 25 m x 5 m transect used for censusing reef fish), the swimming speed of a fish, the length of a fish or other morphometric measures. Research is now focusing on measuring the shape and volume of a fish and in incrementally automating the measurement process.

Stereo-video systems can be modified for use by divers, on Remote Operated Vehicles and sleds and in trawl nets. More recently they have been modified to sample fish assemblages using a remote baited camera station [11,12].

  1. Naiberg, A., Petrell, R. J., Savage, C. R. and Neufeld, T. 1993. Non-invasive fish size assessment method for tanks and sea cages using stereo-video. In: Techniques for Modern Aquaculture (Editor J.K Wang) pp. 372-381. American Society of Agricultural Engineers.
  2. Harvey, E.S., Shortis, M.R., Stadler, M. and M. Cappo. 2002. A comparison of the accuracy and precision of digital and analogue stereo-video systems. Marine Technology Society Journal, 36(2): 38-49.
  3. Li, R., Li, H., Zou, W., Smith, R. G. and Curran, T. A. 1996. An underwater digital photogrammetric system for fishery goematics. International Archives of Photogrammetry and Remote Sensing 31(B5): 524-529.
  4. Petrell, R. J., Shi, X., Ward, R. K., Naiberg, A. and Savage, C. R. 1997. Determining fish size an swimming speed in cages and tanks using simple video techniques. Aquacult. Eng.16: 63-84.
  5. Steeves, G., Peterson, R. and Clark, L. 1998. A quantitative stereoscopic video system for visually measuring the linear dimensions of free-swimming fish. In: Oceans 98 Engineering for sustainable use of the oceans. 28 September-1 October 1998, Nice, France Piscataway. NJ USA IEEE. OES, 3: 1405-1408.
  6. Harvey, E. S., Fletcher, D. and Shortis, M. 2001 a. A comparison of the precision and accuracy of estimates of reef-fish lengths made by divers and a stereo-video system. Fish. Bull. 99(1): 63-71.
  7. Harvey, E. S., Fletcher, D. and Shortis, M. 2001 b. Improving the statistical power of visual length estimates of reef fish: A comparison of estimates determined visually by divers with estimates produced by a stereo-video system. Fish. Bull. 99(1): 72-80.
  8. Harvey, E.S, Fletcher, D., and Shortis, M.R. 2002. Estimation of reef fish length by divers and by stereo-video. A first comparison of the accuracy and precision in the field on living fish under operational conditions. Fisheries Research, 57/3: 257-267
  9. Harvey, E. S. and Shortis, M. 1996. A system for stereo-video measurement of subtidal organisms. MTS J. 29(4): 10-22.
  10. Shortis, M. R. and Robson, S. 2001. VMS Reference and User Guide.
  11. Cappo, M., Speare, P., Wassenberg, T.J., Harvey, E., Rees, M., Heyward, A., and Pitcher, R. Use of Baited Remote Underwater Video Stations (BRUVS) to survey demersal fish: how deep and meaningful? In: Harvey, E.S. and M. Cappo (Eds). Direct sensing of the size frequency and abundance of target and non-target fauna in Australian Fisheries. 4-7 September 2000, Rottnest Island, Western Australia. Fisheries Research and Development Corporation. p 63-71, ISBN 1 74052 057 2.
  12. Cappo. M., Harvey. E., Malcom. H. and P. Speare. 2002 World Congress on Marine Protected Areas. Cairns, August, 2002. Advantages and applications of novel �video fishing� techniques to design and monitor marine protected areas. In Review.

Author

Euan Harvey, University of Western Australia

Related Articles:
« Back to Glossary Index